Molecular Epidemiology of Malassezia globosa and Malassezia restricta in Sudanese Patients with Pityriasis Versicolor

Pityriasis versicolor is a superficial infection of the stratum corneum caused by Malassezia yeasts. The cutaneous Malassezia globosa and Malassezia restricta in Sudanese patients with pityriasis versicolor were elucidated using a molecular-based, culture-independent method and compared with that in healthy individuals. Scale samples were collected by applying an Opsite? transparent dressing to lesional and non-lesional sites on 29 Sudanese patients with pityriasis versicolor and 54 healthy individuals. Malassezia DNA was extracted directly from the samples. The overall level of colonization by Malassezia globosa and Malassezia restricta was analyzed by real-time PCR using a TaqMan probe. The overall level of colonization by Malassezia at the lesional sites was higher than that at the non-lesional sites for all body sites, including the face, neck, cheeks, and trunk (2.7- to 6.0-fold increase). Both M. globosa and M. restricta were detected in patients and healthy individuals. However, M. globosa predominated at lesional sites, whereas the level of colonization by both species was similar in healthy individuals.     

Molecular Identification of <Emphasis Type="Italic">Malassezia</Emphasis> Species in Patients with <Emphasis Type="Italic">Malassezia</Emphasis> folliculitis in Sfax,Tunisia

Aim

Malassezia folliculitis is caused by the invasion of hair follicles by large numbers of Malassezia cells. Several Malassezia researches still use cultures, morphology and biochemical techniques. The aim of this study was to identify Malassezia species isolated from patients diagnosed with folliculitis, at the Parasitology and Mycology Laboratory of Sfax University Hospital, and to explore the genetic diversity of Malassezia by using PCR-RFLP and PCR-sequencing targeting the rDNA region of the Malassezia genome.

Patients and Methods

Specimens were taken from 27 patients with Malassezia folliculitis. For the molecular identification, PCR amplification of the 26S rDNAD1/D2 region was carried out using the Malup and Maldown primers and three restriction enzymes (BanI, MspI and HeaII) for RFLP analysis. The nucleotide sequences of each isolate were compared to those in the NCBI GenBank by using BLASTIN algorithm.

Results

Three species of Malassezia yeasts were identified among the 31 Malassezia strains isolated: M. globosa (83.9%), M. sympodialis (12. 9%) and M. furfur (3.2%). The sequence analysis of M. globosa showed six genotypes.

Conclusion

There is a high genotypic variability of M. globosa colonizing patients with folliculitis.

     

<Emphasis Type="Italic">Malassezia</Emphasis> spp. in Acoustic Meatus of Bats (<Emphasis Type="Italic">Molossus molossus</Emphasis>) of the Amazon Region,Brazil

The yeasts of the Malassezia genus are opportunistic microorganisms and can cause human and animal infections. They are commonly isolated from the skin and auricular canal of mammalians, mainly dogs and cats. The present study was aimed to isolate Malassezia spp. from the acoustic meatus of bats (Molossus molossus) in the Montenegro region, “Rondônia”, Brazil. From a total of 30 bats studied Malassezia spp. were isolated in 24 (80%) animals, the breakdown by species being as follows (one Malassezia sp. per bat, N = 24): 15 (62.5%) M. pachydermatis, 5 (20.8%) M. furfur, 3 (12.5%) M. globosa and 1 (4.2%) M. sympodialis. This study establishes a new host and anatomic place for Malassezia spp., as it presents the first report ever of the isolation of this genus of yeasts in the acoustic meatus of bats.     

Malassezia Intra-Specific Diversity and Potentially New Species in the Skin Microbiota from Brazilian Healthy Subjects and Seborrheic Dermatitis Patients

Malassezia yeasts are part of the resident cutaneous microbiota, and are also associated with skin diseases such as seborrheic dermatitis (SD). The role these fungi play in skin diseases and why they are pathogenic for only some individuals remain unclear. This study aimed to characterize Malassezia microbiota from different body sites in healthy and SD subjects from Brazil. Scalp and forehead samples from healthy, mild SD and severe SD subjects were collected. Non-scalp lesions from severe SD patients were also sampled. 5.8S rDNA/ITS2 amplicons from Malassezia sp. were analyzed by RFLP and sequencing. Results indicate that Malassezia microbiota did not group according to health condition or body area. Phylogenetic analysis revealed that three groups of sequences did not cluster together with any formally described species, suggesting that they might belong to potential new species. One of them was found in high proportions in scalp samples. A large variety of Malassezia subtypes were detected, indicating intra-specific diversity. Higher M. globosa proportions were found in non-scalp lesions from severe SD subjects compared with other areas, suggesting closer association of this species with SD lesions from areas other than scalp. Our results show the first panorama of Malassezia microbiota in Brazilian subjects using molecular techniques and provide new perspectives for further studies to elucidate the association between Malassezia microbiota and skin diseases.     

Prevalencia de especies de Malassezia asociadas a lesiones de dermatitis seborreica en pacientes de Argentina

BackgroundSeborrheic dermatitis (SD) is considered the second most frequently dermatosis associated with the genus Malassezia but little is the knowledge about the epidemiology of this association.AimsTo determinate the prevalence of Malassezia species associated with SD and to analyse their distribution according to the location of the lesion on the body.MethodsThis study was performed in Resistencia city, located in a subtropical area in northeast Argentina. In this study, 226 skin samples from patients with lesions compatible with SD were studied. Age, gender and body sites lesion were recorded. Strains were identified by PCR-RFLP.ResultsOne hundred and thirty-one positive cultures were obtained. Association of 2 species was detected in 10 cases; therefore, 141 strains were isolated. Malasezzia globosa (43.3%) was the most frequent species isolated, followed by Malasezzia furfur (20.6%), Malasezzia sympodialis (17%) and Malasezzia restricta (16.3%). Three isolates of Malasezzia slooffiae (2.1%) and one of Malasezzia pachydermatis (0.7%) were obtained. Statistical significance (P < 0.05) was found between M. globosa and scalp. Malasezzia restricta was isolated only in head areas.ConclusionsThis study suggests M. globosa is the most related species to SD. The prevalence of other species is different from that reported by other authors. Only M. globosa and M. restricta presented a pattern of relationship with the body sites of the lesions. It is noteworthy is the isolation of the zoophylic species M. pachydermatis. The Malassezia genus ecology and the pathogenic role of its species are still under study. This work is a contribution to this knowledge.     

Chemical Organization of the Cell Wall Polysaccharide Core of Malassezia restricta

Malassezia species are ubiquitous residents of human skin and are associated with several diseases such as seborrheic dermatitis, tinea versicolor, folliculitis, atopic dermatitis, and scalp conditions such as dandruff. Host-Malassezia interactions and mechanisms to evade local immune responses remain largely unknown. Malassezia restricta is one of the most predominant yeasts of the healthy human skin, its cell wall has been investigated in this paper. Polysaccharides in the M. restricta cell wall are almost exclusively alkali-insoluble, showing that they play an essential role in the organization and rigidity of the M. restricta cell wall. Fractionation of cell wall polymers and carbohydrate analyses showed that the polysaccharide core of the cell wall of M. restricta contained an average of 5% chitin, 20% chitosan, 5% β-(1,3)-glucan, and 70% β-(1,6)-glucan. In contrast to other yeasts, chitin and chitosan are relatively abundant, and β-(1,3)-glucans constitute a minor cell wall component. The most abundant polymer is β-(1,6)-glucans, which are large molecules composed of a linear β-(1,6)-glucan chains with β-(1,3)-glucosyl side chain with an average of 1 branch point every 3.8 glucose unit. Both β-glucans are cross-linked, forming a huge alkali-insoluble complex with chitin and chitosan polymers. Data presented here show that M. restricta has a polysaccharide organization very different of all fungal species analyzed to date.     

In vitro antifungal efficacy of ciclopirox olamine alone and associated with zinc pyrithione compared to ketoconazole against Malassezia globosa and Malassezia restricta reference strains

The aim of this study was to determine the in vitro fungicidal and growth inhibitory activity of ciclopirox olamine alone (1% and 1.5%) or in association with 1% zinc pyrithione compared to 2% ketoconazole, against Malassezia species particularly involved in the pathogenesis of seborrheic dermatitis. Experiments were performed on Malassezia globosa IP 2387.96 and M. restricta IP 2392.96 strains. Growth inhibitory activity of the active compounds in solution was evaluated by measuring minimal inhibitory concentrations using a broth micro-method and their fungicidal activity by a filtration method after contact times between solutions and yeasts ranging from 3–5 to 30 min. Concerning the determination of minimal inhibitory concentration of ciclopirox olamine/zinc pyrithione, it revealed the marked synergistic inhibitory effect of the association, leading to a higher efficacy compared to ketoconazole. As to the fungicidal activity of ciclopirox olamine, it significantly increased with the contact time. After 15–30 min of contact between 1.5% ciclopirox olamine and Malassezia strains, a 2-log reduction of Malassezia counts was observed. The 1.5% ciclopirox olamine/1% zinc pyrithione association was characterized by a steady fungicidal efficacy whereas the 2% ketoconazole solution did not express any fungicidal effect. In conclusion, this study demonstrates the in vitro inhibitory and fungicidal efficacy of the ciclopirox olamine/zinc pyrithione association against Malassezia species and underscores its potential interest in the treatment of seborrheic dermatitis.     

Main rhizosphere characteristics of the Cd hyperaccumulator Rorippa globosa (Turcz.) Thell

Aim

This article was aimed to explore the main rhizospherial properties of the Cd hyperaccumulator R. globosa compared to those of the non hyperaccumulator Rorippa palustris (Leyss.) Bess. representing the same genus (Rorippa) of Cruciferae.

Method

Pot culture experiments using soil spiked with Cd as CdCl₂·2.5H₂O and rhizobags were conducted to determine the differences in Cd accumulation vs. pH, dissolved organic carbon (DOC), Cd chemical fractionation, enzyme activities, and microorganism number in the rhizospheres of R. globosa and R. palustris, and in the bulk soils.

Results

Experiments on Cd uptake by R. globosa and R. palustris from soil spiked with different doses of Cd ranging from 0 to 40 mg?kg^?1, confirmed Cd-hyperaccumulating properties of R. globosa (Cd accumulation in the above-ground organs >100 mg kg^?1, enrichment factor EF> 1, translocation factor TF> 1, no significant biomass reduction at Cd doses >10 mg kg^?1) and the lack of such properties in R. palustris, which made these species suitable for comparative studies. The pH value was found to be a constant, specific property of the rhizosphere of R. globosa and R. palustris, and of the bulk soil, independent on the Cd dose, however the differences were rather small: by 0.2 unit lower in the rhizosphere of R. globosa, and only by 0.1 unit lower in the rhizosphere of R.. palustris compared to the bulk soil. Chemical fractionation of Cd, i.e. its affinity to pools of different binding strength, also appeared to be a specific feature of a rhizosphere and soil independent on the Cd dose. It exhibited a unique capability of the rhizosphere of the Cd-hyperaccumulator R. globosa to mobilize Cd, which enriched the most labile exchangeable fraction in 24.4 % and the immobile residual fraction in 42.3 %, compared to 19.3 % and 50.8 % in the bulk soil and in the rhizosphere of the non-hiperaccumulator R.palustris that did not show significant difference (p?<?0.05) from the bulk soil. In turn, DOC concentrations, enzymatic (urease and catalase) activity and microorganism (bacteria, fungi and actinomycetes) growth in rhizosphere soils were largely influenced by different Cd doses, although they were always considerably higher in the rhizosphere soils of R globosa, than in the rhizosphere of R. palustris and in the bulk soil, in particular at Cd doses ≥10 mg kg^?1.

Conclusion

pH and DOC changes in the rhizosphere of the Cd-hyperaccumulator R. globosa were found to be of a minor importance. The alteration of Cd chemical fractionation consisting in substantial reduction of the immobile residual pool and Cd enrichment primarily in the most labile exchangeable fraction, along with over 2-fold higher number of microorganisms was considered to be the driving force of Cd hyperaccumulation.     

Genotype Analyses of Human Commensal Scalp Fungi,Malassezia globosa,and Malassezia restricta on the Scalps of Patients with Dandruff and Healthy Subjects

Dandruff and seborrheic dermatitis are common afflictions of the human scalp caused by commensal scalp fungi belonging to the genus Malassezia. Malassezia globosa and Malassezia restricta are the predominant species found on the scalp. The intergenic spacer regions of these species’ rRNA genes contain short sequence repeats (SSR): (GT)n and (CT)n in M. globosa and (CT)n and (AT)n in M. restricta. In the present study, we compared the genotypes (SSR) of M. globosa and M. restricta colonizing the scalps of patients with dandruff and healthy individuals. For M. globosa, the genotype (GT)₁₀:(CT)₈ (40.3 %, 25/62) was predominant followed by (GT)₉:(CT)₈ (14.5 %, 9/62) and (GT)₁₁:(CT)₈ (14.5 %, 9/62) in patients with dandruff, whereas the genotypes in healthy subjects were diverse. For M. restricta, the genotype (CT)₆:(AT)₆ (59.7 %, 37/62) was predominant followed by (CT)₆:(AT)₈ (24.2 %, 15/62) in patients with dandruff, while four genotypes, (CT)₆:(AT)₆ (10.5 %, 6/57), (CT)₆:(AT)₇ (22.8 %, 13/57), (CT)₆:(AT)₈ (17.5 %, 10/57), and (CT)₆:(AT)₁₀ (21.1 %, 12/57), accounted for 71.9 % of all combinations in healthy subjects. The results of this study suggest that the M. globosa genotype (GT)₁₀:(CT)₈ and the M. restricta genotype (CT)₆:(AT)₆ may be involved in the development of dandruff.     

Association of Malassezia to Atopic Dermatitis

Purpose of Review

Atopic dermatitis (AD) is a common chronic, inherited, relapsing, inflammatory skin condition. A multifactorial etiology has been postulated, including genetic and immunological factors, impaired skin barrier function and environmental triggers, all of them are relevant in the pathogenesis. Malassezia spp. is the most common fungi of the skin microbiome. Most of the studies comparing the skin colonization with Malassezia spp. in healthy people and AD patients did not show difference between both groups. This review aims to show the studies carried out in this regard and the reported evidence about the role of Malassezia spp. in the pathogenesis of AD.

Recent Findings

The rate of IgE-mediated sensitization Malassezia spp. is very high in AD patients, mainly in adult patients and in patients with involvement in the head and neck. Different mechanisms have been postulated to explain the interaction of Malassezia spp. with human skin cells and immune cells and how its interaction contributes to the inflammation process in AD. Systemic and topical azole antifungals have been used with doubtful results showing beneficial effects in some AD patients.

Summary

There is no clear explanation for the high frequency of Malassezia spp. sensitization in AD patients in relation with healthy individuals. Further research is necessary to determine the specific role of Malassezia in AD and the indication for the use of antifungals in this disease.

     

Phosphate-solubilizing soil yeast Meyerozyma guilliermondii CC1 improves maize (Zea mays L.) productivity and minimizes requisite chemical fertilization

Aim

Phosphate-solubilizing yeasts have been under-exploited in eco-friendly maize cultivation. In this regard, soil yeasts Meyerozyma guilliermondii CC1, Rhodotorula mucilaginosa CC2 and M. caribbica CC3 were investigated for their plant growth-promoting (PGP) activities.

Methods

Soil yeasts were isolated and characterized. Maize (Zea mays L. cv. Tainong No.1) and Chinese cabbage (Brassica rapa L. cv. Pekinensis) were used for seed bioassay. Growth-promoting effects of yeasts under greenhouse conditions were evaluated using maize and lettuce (Lactuca sativa L. cvs. Capitata and Taiwan sword leaf). Ultimately, M. guilliermondii CC1 was tested on field-grown maize; treatments included full-dose chemical fertilizers (CF), yeast (CC1), half-dose chemical fertilizers (½CF), CC1?+?½CF and control. Nutrient uptake, growth, and yield of maize and rhizospheric soil microbes were estimated.

Results

Strain M. guilliermondii CC1 exhibited better seed vigor index in maize and Chinese cabbage. CC1?+?½CF significantly improved the dry-weights, and nutrient uptakes of maize and sword leaf lettuce under greenhouse conditions. In field, CC1?+?½CF application exerted a pronounced effect on growth of maize, cob yield, nutrient-uptake and rhizospheric soil microbial counts.

Conclusion

Our results validated superior biochemical potency and PGP traits of M. guilliermondii CC1 that reduced requisite chemical fertilizer application without affecting the optimal productivity in maize.     

Pityriasis Versicolor: Clinical Spectrum and Diagnosis

Pityriasis versicolor (PV) is caused by the fungus Malassezia, especially by Malassezia globosa. The predisposing factors for PV are heat, humidity, hyperhidrosis, oral contraceptives, stress, application of oily preparations, and treatment with corticosteroids. PV is found mainly on the seborrheic areas of the trunk, shoulders, upper aspects of the arms, and neck, but it may spread to the face, scalp, submammary areas, axillae, groin, skin folds, and buttocks. It is characterized by hyperpigmented, hypopigmented, or erythematous (versicolor), round-to-oval, finely scaling, thin plaques. Other less frequent clinical variants are papular, atrophic, imbricata, and pityriasis rubra pilaris-like presentations. The diagnosis of PV is usually made clinically with the aid of Wood’s light or dermoscopy. Direct microscopic examination, culture, biopsy, and molecular studies are among the laboratory diagnostic methods. Topical therapy is the treatment of choice for most patients. Systemic imidazole therapy is usually reserved for widespread or resistant cases.     

Molecular Analysis of Malassezia Microflora from Patients with Pityriasis Versicolor

Background: Pityriasis versicolor (PV) is a superficial infection of the stratum corneum caused by Malassezia species. Eleven species have been identified within this genus, namely M. globosa, M. restricta, M. sympodialis, M. furfur, M. obtusa, M. slooffiae, M. pachydermatis, M. dermatis, M. japonica, M. yamatoensis, M. nana. M. furfur has long been identified as the causative fungus of PV. However, recent studies using the culture and isolation identified by morphological and physiological characteristics suggest that M. globosa is the causative agent of PV. Objectives: The aim of this study was to examine the distribution of PV microorganisms with a molecular-based non-culture method. Patients: The subjects were 49 patients with PV (32 males, 17 females; 16–83 years old) who visited our outpatient clinic. Methods: Samples were taken from lesions for direct microscopy with methylene blue and detected Malassezia species without M. pachydermatis and M. nana using a non-culture-based method consisting of nested PCR with specific primers. Results: The most frequently isolated species were M. globosa and M. restricta (both 93.9%). Only M. globosa was detected from the lesion in which the mycelial form alone was observed microscopically, but M. restricta was not. Conclusions: Our results suggest that M. globosa is the causative agent of PV.     

Occurrence and Characterization of Candida nivariensis from a Culture Collection of Candida glabrata Clinical Isolates in Malaysia

Background

Candida nivariensis and C. bracarensis have been recently identified as emerging yeast pathogens which are phenotypically indistinguishable from C. glabrata. However, there is little data on the prevalence and antifungal susceptibilities of these species.

Objective

This study investigated the occurrence of C. nivariensis and C. bracarensis in a culture collection of 185 C. glabrata isolates at a Malaysian teaching hospital.

Methods

C. nivariensis was discriminated from C. glabrata using a PCR assay as described by Enache-Angoulvant et al. (J Clin Microbiol 49:3375–9, 2011). The identity of the isolates was confirmed by sequence analysis of the D1D2 domain and internal transcribed spacer region of the yeasts. The isolates were cultured on Chromogenic CHROMagar Candida ^® agar (Difco, USA), and their biochemical and enzymic profiles were determined. Antifungal susceptibilities of the isolates against amphotericin B, fluconazole, voriconazole and caspofungin were determined using E tests. Clotrimazole MICs were determined using a microbroth dilution method.

Results

There was a low prevalence (1.1 %) of C. nivariensis in our culture collection of C. glabrata. C. nivariensis was isolated from a blood culture and vaginal swab of two patients. C. nivariensis grew as white colonies on Chromogenic agar and demonstrated few positive reactions using biochemical tests. Enzymatic profiles of the C. nivariensis isolates were similar to that of C. glabrata. The isolates were susceptible to amphotericin B, fluconazole, voriconazole and caspofungin. Clotrimazole resistance is suspected in one isolate.

Conclusion

This study reports for the first time the emergence of C. nivariensis in our clinical setting.     

Temperature regulation of floral buds and floral thermogenicity in Magnolia denudata (Magnoliaceae)

Key message

The gynoecium in M. denudata was thermogenic, and the first peak in the female phase lasted longer than the second peak in the male phase during flowering.

Abstract

The floral biology of Magnolia denudata, including the thermogenesis of floral buds and blooming, were investigated using a portable infrared thermal imaging radiometer and digital infrared thermometer. We found that M. denudata buds have extremely dense trichomes that maintain internal temperatures above external temperatures. The pattern of thermogenesis in M. denudata anthesis consisted of two distinct episodes corresponding to apparent receptivity of the stigmas in the female phase and incipient shedding of pollen in the male phase: one begins in the female phase and lasts about 6 h and another occurs synchronously 24 h later and lasts about 4 h in the male phase. In addition, we found that the temperature was significantly elevated in the inner petals upon flowering, indicating that they may play an important role in producing a warm floral chamber. These results increase our understanding of the strategies used by Magnoliaceae blossoms to maintain an optimal microclimate at low temperatures in the early spring.     

Prevalence of Malassezia species in pityriasis versicolor lesions in northeast Argentina

BackgroundMalassezia species normally colonize the skin but they can change their saprophytic state and invade the stratum corneum as pathogens.AimsTo determine the prevalence of Malassezia species isolated from patients with pityriasis versicolor (PV) and to analyse their distribution according to the location of the lesion on the body.MethodsThis study included 218 patients with PV and positive Malassezia cultures who resided in the city of Resistencia, a subtropical area located in northeast Argentina. Age, gender, and the body site of lesions were recorded. Strains were identified by PCR-RFLP.ResultsMalassezia sympodialis (37.7%) and Malassezia globosa (37.2%) were the most prevalent species isolated alone or in association with other Malassezia species in 82% of the patients. Malassezia furfur (21.3%) was the third most common species, followed by Malassezia slooffiae (1.7%), and Malassezia restricta (1.3%), which was found only in combination with M. globosa and M. sympodialis. Malassezia dermatis (0.4%) and Malassezia pachydermatis (0.4%) were each isolated once. None of the species affected a body site with statistical significance. Significant difference between genders according to age was found only in the 31–40-year-age group.ConclusionsThis study suggests that M. sympodialis and M. globosa represent the main species implicated in the pathogenicity of PV. M. furfur appears to be the third agent of importance in this geographical area. Statistical analyses showed none of the species was particularly associated with any one of the body sites.     

Isolation of Malassezia globosa and M. sympodialis from patients with pityriasis versicolor in Spain

Pityriasis versicolor is a superficial infection of the stratum corneum by several yeast species formerly collectively named Malassezia furfur. The genus Malassezia has been recently enlarged with new species. With the exception of M. pachydermatis, the remaining six species have an absolute requirement in vitro for supplementation of long-chain fatty acids in media. These lipophilic yeasts comprise six species: M. furfur, M. globosa, M. obtusa, M. restricta, M. slooffiae and M. sympodialis. The aim of this study was to establish whether there was any association between the various species of Malassezia and pityriasis versicolor lesions. Thus, we studied the isolates from 79 patients with pityriasis versicolor, both from lesions and from apparently healthy skin close to the visible lesions. In pityriasis versicolor lesions, the species most frequently isolated was M. globosa (90%), followed by M. sympodialis (41%). Almost all isolates (99%) belonged to one of these two species. The most frequent pattern was M. globosa as the sole species (58% of cases), although the association with M. sympodialis was also frequent (30%). These results confirmed M. globosa as the main agent of pityriasis versicolor and M. sympodialis as the second agent in importance. Malassezia globosa was found to be a species with high levels of esterase and lipase enzymes of probable importance in their pathogenicity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Reducing basal salicylic acid enhances Arabidopsis tolerance to lead or cadmium

Aims

Phytoremediation is an emerging strategy for the removal of heavy metal contaminants. However, one of the prerequisite is to understand adequately plant resistant mechanisms. The present study was performed to assess the role of endogenous SA in plant response to Pb or Cd using wild-type (wt) Arabidopsis and its SA-accumulating mutant snc1, SA-reducing transgenic line nahG, SA signal-blocking npr1-1, and snc1/nahG (i.e. expression of nahG in snc1 plant) with a comparable level of SA to the wt.

Methods

Plants were grown hydroponically in controlled conditions. For heavy metal exposure, Pb²⁺ or Cd²⁺ at final concentrations of 50 μM, 100 μM, and 150 μM, respectively, was added to the culture solution. Unless otherwise indicated, samples were harvested after 7 d of exposure, and used for analyses.

Results

Compared to the wt level, the high endogenous SA significantly potentiated Pb- and Cd-induced plant growth retardation, whereas SA deficiency decreased the growth inhibition, and SA signaling blockage also had some protective effect. The expression of nahG in snc1 plant mitigated effectively the growth inhibition. The SA-related mechanism was involved in redox homeostasis, photosynthetic process, and soluble matter accumulation.

Conclusions

These results suggest that Pb- or Cd-induced phytotoxicity in Arabidopsis was intensified by elevated endogenous SA, whereas ameliorated by reduced SA.     

Endogenous nitric oxide generation in protoplast chloroplasts

Key message

NO generation is studied in the protoplast chloroplasts. NO, ONOO ^? and ROS (O ₂ ^? and H ₂ O ₂ ) are generated in chloroplasts. Nitric oxide synthase-like protein appears to be involved in NO generation.

Abstract

Nitric oxide stimulates chlorophyll biosynthesis and chloroplast differentiation. The present study was conducted to better understand the process of NO generation in the leaf chloroplasts and protoplasts. NO, peroxynitrite and superoxide anion were investigated in the protoplasts and isolated chloroplasts using specific dyes, confocal laser scanning and light microscopy. The level of NO was highest after protoplast isolation and subsequently decreased during culture. Suppression of NO signal in the presence of PTIO, suggests that diaminofluorescein-2 diacetate (DAF-2DA) detected NO. Detection of peroxynitrite, a reaction product of NO and superoxide anion, further suggests NO generation. Moreover, generation of NO and peroxynitrite in the chloroplasts of wild-type Arabidopsis and their absence or weak signals in the leaf-derived protoplasts of Atnoa1 mutants confirmed the reactivity of DAF-2DA and aminophenyl fluorescein to NO and peroxynitrite, respectively. Isolated chloroplasts also showed signal of NO. Suppression of NO signal in the presence of 100 μM nitric oxide synthase inhibitors [l-NNA, Nω-nitro-l-arginine and PBIT, S,S′-1,3-phenylene-bis(1,2-ethanediyl)-bis-isothiourea] revealed that nitric oxide synthase-like system is involved in NO synthesis. Suppression of NO signal in the protoplasts isolated in the presence of cycloheximide suggests de novo synthesis of NO generating protein during the process of protoplast isolation. Furthermore, the lack of inhibition of NO production by sodium tungstate (250 μM) and inhibition by l-NNA, and PBIT suggest involvement NOS-like protein, but not nitrate reductase, in NO generation in the leaf chloroplasts and protoplasts.     

A novel elicitor identified from Magnaporthe oryzae triggers defense responses in tobacco and rice

Key message

Our studies indicate a potential important elicitor candidate which can aid in the fight against a worldwide disease, rice blast.

Abstract

In this study, we report the purification, identification, characterization, and gene cloning of a novel hypersensitive response-inducing protein elicitor (MoHrip2) secreted from an important pathogenic fungus, Magnaporthe oryzae. The protein fraction was isolated from the culture filtrate of M. oryzae and identified by de novo sequencing. The elicitor-encoding gene mohrip2 was cloned following sequence comparison and PCR amplification. This 459-bp gene encodes a 152-residue polypeptide that contains an 18-residue signal peptide and exhibits a pI of 4.72 and an apparent molecular mass of 16 kDa. The hypothetical protein, MoHrip2, was expressed in Escherichia coli, and both the recombinant and the endogenous protein caused necrotic lesions in tobacco leaves. In addition to phenolic compound deposition and alkalization of the extracellular medium, MoHrip2 also induced hydrogen peroxide production and nitric oxide accumulation in tobacco cells. Moreover, rice seedlings treated with MoHrip2 exhibited pronounced resistance to M. oryzae compared with control seedlings.